JP2000329141A - Bearing structure having conducting mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing structure with a non-contact rotation capable of certainly escaping an static electricity generated at a rotation side member to a fixed side member. SOLUTION: A magnetic fluid 13 is interposed between a rotation side member and a fixed side member constituting a bearing on a rotation center axis or therearound such that a relative rotation speed is minimized between both members or at an area where a stream of suction or discharge of a gas required for a dynamic pressure generation of a bearing does not exist or can be neglected. The static electricity generated at the rotation side member is gradually conducted to the fixed side member. As another embodiment, a portion or a whole of a bearing portion constitution element is made of conductive ceramics with an excellent anti-abrasion property such as Al2O3-30 vol.% TiC, TiB2, Si3N4-30 vol.% TiN. The static electricity is escaped by a contact between these elements at the time of rotation stopping.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing structure for a spindle motor used for driving a small storage device such as a hard disk or a bar code reader.
In particular, the present invention relates to a bearing structure having a conduction mechanism for releasing static electricity.

[0002]

2. Description of the Related Art Small storage devices such as hard disks,
Spindle motors used for driving bar code readers, etc., require small size, high precision, and high rotation, and their bearings require a dynamic pressure that provides more stable rotation than conventional ball bearings. Bearings are becoming used. Above all, the dynamic pressure gas bearing uses the gas dynamic pressure generated between the relatively rotating members as a bearing, and rotates in a non-contact state between the bearing members, so that a higher speed rotation is possible, and the liquid dynamic It has advantages such as easy handling compared to pressure.

However, a disadvantage of the gas bearing that rotates in a non-contact state as described above is that the rotating member may generate static electricity due to the influence of air friction or the like. Due to the contact, the static electricity cannot be released to the bearing fixing member side. Therefore, the static electricity causes a discharge to occur between the recording medium mounted on the rotating member side and the head for writing and reading information. As a result, there is a risk of damaging these devices.

[0004] Even in such a gas bearing, when rotation stops, the rotating side member and the fixed side member constituting the bearing portion come into contact with each other. It is possible to discharge static electricity. However, if these members are made of a material such as non-conductive ceramics, the static electricity cannot be released even when both members come into contact with each other at the time of stoppage. If the operation of the contact continues for a long time and the static electricity is accumulated, the same problem as described above occurs.

Japanese Patent Application Laid-Open No. 11-55916 discloses a means for avoiding the above problem, and FIG. 4 shows the contents thereof. In the figure, reference numeral 41 denotes a housing. A 42 shaft is fixed to the housing 41. A 43 rotor hub is fitted to the shaft 42, and a hard disk (not shown) is mounted on an outer peripheral surface of the rotor hub 43. . A fixed-side radial bearing 44 is fixed to the shaft 42, and a rotating-side radial bearing 45 is fixed to the rotor hub 43. Both of them are opposed to each other with a predetermined gap. Numerals 46 and 47 in the figure denote thrust bearings, which are opposed to each other at predetermined lower and upper end surfaces of the fixed-side radial bearing 44, respectively. 48 is a stator, 4
9 is a rotor magnet.

[0006] The operation of the spindle motor thus configured is such that when a coil of the stator 48 is energized, a rotational driving force is generated between the stator 48 and the rotor magnet 49, whereby the rotor hub to which the rotor magnet 49 is attached is attached. 4
3 rotates. Due to this rotation, the rotating radial bearing 45 fixed to the rotor hub 43 rotates, and a radial dynamic pressure is generated between the rotating radial bearing 45 and the fixed radial bearing 44 facing the rotating radial bearing 45. Since thrust dynamic pressure is generated between the lower end face and the upper end face of the opposed fixed-side radial bearing 44, the rotor hub 43 and the members fixed thereto are fixed to the shaft 42 and other fixed-side members. It rotates without contact.

In order to release static electricity accumulated in the rotating member rotating in a non-contact manner, in this apparatus, the magnet 51 and the magnetic plate 52 are attached to the rotor hub 43 in close contact with each other, and the magnetic plate 52 and the magnetic plate 52 are fixed to each other. A slight gap is provided between the surface facing the shaft 42 and the gap is filled with a magnetic fluid 53, so that static electricity is supplied between the rotating member and the fixed member between the two members. This is ensured through the magnetic fluid 53.

[0008]

However, Japanese Patent Application Laid-Open No.
The above-described configuration disclosed in Japanese Patent No. 55916 has a problem. First, the radial dynamic pressure generating section (between 44 and 45) and the thrust dynamic pressure generating section (between 44 and 46, and between 44 and 47) which constitute this bearing are connected to each other for the conduction of air for generating dynamic pressure. The air suction / discharge port is only located at the upper end opening and the lower rotor hub 43 and the housing 41 as shown by the arrow 50 in the drawing, and thus the flow of the dynamic pressure generating air is As will be apparent, it penetrates the magnetic fluid sealing layer. For this reason, depending on the dimensions of the bearing portion, the conditions of use of the bearing, the properties of the sealing member used, and the like, there is a possibility that the magnetic fluid sealing layer is broken by the penetration of the inflowing air and the magnetic liquid 53 is scattered. .

As another problem, when the peripheral speed of the bearing rotating member sealed by the magnetic fluid is increased to a certain degree or more by rotation, the viscous resistance of the magnetic fluid filled between the fixed member and the rotating member is reduced. The problem is that the torque increases with the increase in the resistance, and as a result, the power consumption increases. Furthermore, since the viscous resistance causes heat generation, the advantage of using a hydrodynamic gas bearing may be impaired.

In the case where generally non-conductive ceramics having high wear resistance are used for the bearing portion, static electricity accumulated in the rotating member is fixed even when the bearing portion is in contact when the rotation is stopped. It cannot escape to the side member.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and even in a bearing that performs non-contact rotation, static electricity generated in the rotating member during rotation is reliably applied to the fixed member. The present invention provides a relief bearing structure. Also,
It is an object of the present invention to provide a bearing which is capable of conducting static electricity due to the contact in a state where both members are in contact with each other when the rotation is stopped, and is excellent in wear resistance and rigidity.

[0012]

The present invention according to claim 1 comprises a fixed side member and a rotating side member, and when the rotating side member rotates, the fixed side member connects the rotating side member. In a bearing structure supported in a non-contact state, a magnetic fluid is interposed between the two members on or near the rotation center axis of the rotation where the relative rotation speed between the two members is minimized, and the rotation is performed during rotation. It is characterized in that a mechanism is provided for conducting static electricity generated in the side member to the fixed side member as needed.

The bearing structure according to the second and fifth aspects of the present invention is characterized in that the means for supporting the rotating-side member when the fixed-side member is not in contact is a hydrodynamic gas bearing. I have.

According to a third aspect of the present invention, the fixed member includes a fixed member and a rotating member. When the fixed member is rotated, the fixed member is connected to the fixed member by dynamic pressure gas bearing means. In a bearing structure that is supported in a non-contact state, a magnetic fluid is interposed between the two members in a region where there is no or negligible gas flow of suction or discharge of gas required for generating the dynamic pressure, and the rotation side during rotation is rotated. It is characterized in that a mechanism is provided for conducting static electricity generated in the member to the fixed side member as needed.

According to a fourth aspect of the present invention, a stationary member and a rotating member are provided. When the rotating member rotates, the stationary member supports the rotating member in a non-contact state. In the bearing structure, part or all of the elements constituting the bearing portion of the two members are made of conductive ceramics, and when the rotation stops, the elements constituting the bearing portion come into contact with each other. It is characterized in that a mechanism for releasing the accumulated static electricity to the fixed side member is provided.

In the bearing structure according to the present invention, the material of the conductive ceramic is Al _{2
0 3 -30vol% TiC, TiB 2} , Si 3 N 4 -30v
ol% TiN.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment according to the present invention will be described with reference to the drawings. FIG. 1 shows a hydrodynamic gas bearing according to this embodiment. In the drawing, reference numeral 1 denotes a housing, 2 denotes a shaft fixed to the housing, and an outer periphery of the shaft 2 rotates around the shaft 2. 3 rotor hubs are fitted. Between the shaft 2 and the rotor hub 3, a fixed radial bearing 4 which is a member constituting a gas bearing portion is fixed to the shaft 2 and a rotating radial bearing 5 is fixed to the rotor hub 3; They face each other with a predetermined gap. A disk-shaped thrust bearing 6 is further mounted on the outer periphery of the shaft 2 perpendicularly to the axis of the shaft 2, and this thrust bearing is provided with a thrust dynamic pressure generation groove indicated by a dotted line 7. It faces the lower end surface of the rotation side radial bearing 5.

A yoke 11 is mounted at the center of the upper end surface of the shaft 2 in the drawing.
A yoke 12 is also attached to a position opposing the yoke. The yokes 11 and 12 oppose each other at a predetermined interval, and a space between them is filled with 13 magnetic fluids.
Similarly, an annular magnet 14 is fixed to the outer periphery of the yoke 11 on the upper end surface of the shaft 2 and restrains the magnetic fluid 13 at that position.

Fifteen stators are radially fixed to the housing 1 and face 16 rotor magnets mounted on the inner peripheral surface of the rotor hub 3. The rotor hub 3
A plurality of recording media (not shown) are mounted around the recording medium.

The operation of the hydrodynamic gas bearing according to the above-described configuration is as follows. When a coil wound around the outer periphery of the stator 15 is energized, an attractive / repulsive force is generated between the stator 15 and the rotor magnet 16. This action allows the rotor magnet 16
The rotor hub 3 integrated therewith rotates around the shaft 2. Along with this rotation, a radial dynamic pressure is generated between the radial bearings 4 and 5 provided between the shaft 2 and the rotor hub 3, and a thrust dynamic pressure is generated between the thrust bearing 6 and the lower end surface of the radial bearing 5. As a result, the rotor hub 3 and the other rotating members rotate without contact with the shaft 2 and other rotating members.

In the rotating state of the rotor hub 3, since the place where the magnetic fluid 13 is provided is located at the center axis of the rotation, there is substantially no relative movement between the shaft 2 and the rotor hub 3. Further, as described above, the rotation of the rotor hub 3 is supported by the hydrodynamic gas bearing, but there is no airflow at the place where the magnetic fluid 13 exists. From the above, the contact state of the magnetic fluid 13 interposed across the shaft 2 and the rotor hub 3 is extremely stable, and thus, the static electricity generated on the rotating member side is maintained even when the rotor hub 3 is rotating. Thus, the magnetic fluid 13 can be reliably released to the shaft 2 at any time.

The material of each of the above members is, for example, that the shaft 2 and the rotor hub 3 are capable of releasing static electricity as a conductor such as stainless steel. It is preferable to use ceramics such as alumina having excellent wear and rigidity.

Next, a second embodiment according to the present invention will be described with reference to the drawings. FIG. 2 shows a cross section of the gas bearing according to the present embodiment. In the drawings, the same components as those described in the above embodiment are denoted by the same reference numerals, and description thereof will be omitted. In the figure, 24 is a fixed radial bearing, 25 is a rotating radial bearing, and 26 is a thrust bearing. These 24, 2
The bearing materials 5 and 26 are different from the previous embodiment in that they are conductive ceramics. In other respects, it is the same as the previous embodiment except that no magnetic fluid is provided.

In the present embodiment, while the ceramics having excellent wear resistance and rigidity, which are preferable for the bearing, are used for the dynamic pressure bearing portion, when the rotation is stopped, the bearing portion comes into contact with the rotating side member, so that the rotating side member is contacted. The stored static electricity is discharged through the contacting bearing members. For this reason, conductive ceramics are used for the bearings 24, 25, and 26. More specifically, the ceramic bearings are made of Al ₂ O ₃ -30 vol% TiC having conductivity and high wear resistance. , TiB ₂ , S
It is formed of ceramics such as i ₃ N ₄ -30 vol% TiN.

In this embodiment, a means for releasing the accumulated static electricity at the time of stoppage is provided. Therefore, the static electricity releasing mechanism using the magnetic fluid at the time of rotation, which is provided in the previous embodiment, is not attached. Of course, it is also possible to provide a similar mechanism. In addition, the ceramic bearing 24 made of the above-mentioned material is fixed to the shaft 2 which is usually made of stainless steel. However, as an alternative, the conductive ceramic including the shaft 2 may be used. Also in this case, by providing the magnetic fluid mechanism, static electricity can always be released through the conductive ceramics even during rotation.

In this embodiment, all the members 24, 25 and 26 constituting the bearing portion are replaced with a conductive ceramic material. However, when the rotation is stopped, the contact between the rotating member and the fixed member is stopped. It is only necessary that only the member that can reliably obtain the electric conductivity be electrically conductive.
As long as the structure 5 and the thrust bearing 26 can be reliably contacted at the time of a stop, both are made conductive, and the fixed-side radial bearing 24 does not necessarily need to be made of a conductive material.

Next, a dynamic bearing according to a third embodiment of the present invention will be described with reference to the drawings. FIG.
FIG. 3 shows a cross section of the bearing structure according to the present embodiment,
The same components as those described in the above embodiments are denoted by the same reference numerals, and description thereof will be omitted. The present embodiment differs from the previous embodiments in that the shaft rotates and is supported by the fixed sleeve.

In the figure, 21 is a cylindrical sleeve 31
The shaft 32 is fitted into the sleeve 31 of the housing. 33 rotor hubs are attached to the shaft 32, and these constitute a rotation side member. On the inner peripheral surface of the sleeve 31, 34 fixed-side radial bearings are attached, and a predetermined gap is provided to support the shaft 32. This shaft 32 is conductive,
It is preferably made of conductive ceramics. Alternatively, a ceramic sleeve may be extrapolated around the shaft 32 to face the fixed-side radial bearing 34.
A thrust bearing 36 is mounted below the upper end surface of the rotor hub 33, and a thrust dynamic pressure generating groove 7 indicated by a dotted line is provided on a lower surface of the thrust bearing 36 so as to face the fixed-side radial bearing 34. are doing. Between the lower end surface of the shaft 32 in the drawing and the upper surface of the housing 21 opposed thereto, there is provided a mechanism in which the magnetic fluid 13 similar to that of the first embodiment is interposed.

The operation of the spindle motor configured as described above is such that the rotor hub 33 and the shaft 32 rotate by the rotational driving force generated between the stator 15 and the rotor magnet 16, and between the shaft 32 and the radial bearing 34. The radial dynamic pressure is increased between the fixed radial bearing 34 and the thrust bearing 3.
As a result, thrust dynamic pressure is generated between the rotating member 6 and the rotating member in a non-contact manner with respect to the stationary member. During this time, static electricity generated on the rotating member side is released to the fixed member side as needed through the magnetic liquid 13 interposed between the two.

Although not shown in the drawings, the conduction mechanism using the magnetic fluid is connected to a shaft 3 which is the central axis of rotation.
2 is not provided in the center of the lower end face,
It may be provided on the cylindrical outer peripheral surface near the lower end. That is, a donut-shaped member is attached to the sleeve 31, and the shaft 3 is inserted into a hollow portion of the donut-shaped member.
2, a gap may be provided between the two, and the gap may be filled with a magnetic fluid to form an electrostatic conduction mechanism. In this case, since the rotational peripheral speed of the shaft 32 acts on the magnetic fluid, the problem of resistance and heat generation due to the viscosity of the magnetic fluid 13 as described above remains, but if the configuration shown in FIG. Since there is no air passage for generating the gas dynamic pressure as described in the description of the prior art, it is possible to sufficiently exert the function of releasing static electricity under certain conditions.

As described above, the bearing structure according to the present invention has been described with reference to the respective embodiments. However, all of the above description relates to the hydrodynamic gas bearing. However, the present invention is not limited to this, and can be applied to other bearing structures that rotate in a non-contact manner, such as a magnetic bearing structure and a hydrostatic gas bearing structure. That is, even in these other bearing structures, static electricity is released by using a magnetic fluid at a position where there is no air flow and there is substantially no relative rotation (center region of rotation), and / or a conductive ceramic material is used. It is possible to discharge static electricity when the rotation is stopped by using the above bearing, and these configurations are also included in the scope of the present invention.

[0032]

In the bearing structure according to the present invention, the magnetic fluid having conductivity is interposed between the rotating side member and the fixed side member constituting the bearing portion, so that the rotating side member can rotate even during rotation. The static electricity generated on the rotating member side can be released to the fixed member side as needed.

The magnetic fluid is disposed at a position where the flow of air passing through the inside of the bearing is almost negligible, so that the magnetic fluid interposed between the rotating member and the fixed member is reduced by the air flow. It can be prevented from being blown or scattered.

Further, by arranging the magnetic fluid on or near the rotation center axis of the rotating member where the influence of the relative peripheral speed between the members constituting the bearing can be almost neglected, especially in the high speed rotation region. The increase in the viscous resistance of the magnetic fluid and the accompanying heat generation can be suppressed.

According to another embodiment, the gas bearing is formed from ceramics having conductivity, so that the high rigidity and good wear resistance of ceramics, which are favorable characteristics for the bearing, can be utilized. In addition, static electricity accumulated in the rotating member when the rotation is stopped can be released to the fixed member in contact with the rotating member.

[Brief description of the drawings]

FIG. 1 is a sectional view of a bearing structure according to an embodiment of the present invention.

FIG. 2 is a sectional view of a bearing structure according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view of a bearing structure according to another embodiment of the present invention.

FIG. 4 is a sectional view of a conventional bearing structure.

[Explanation of symbols]

 Reference Signs List 2 shaft 3 rotor hub 4 fixed-side radial bearing 5 rotating-side radial bearing 6 thrust bearing 13 magnetic fluid 14 magnet 24 fixed-side radial bearing 25 rotating-side radial bearing 26 thrust bearing 31 sleeve 32 shaft 33 rotor hub 34 fixed-side radial bearing 36 thrust bearing

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kaoru Murabe 1-1-1 Kunyokita, Itami City, Hyogo Prefecture F-term in Sumitomo Electric Industries, Ltd. Itami Works 3J011 AA04 AA20 BA02 BA08 CA02 JA03 KA04 MA21 RA04 SD01 SD03 SD04 SD10 5H607 BB01 BB14 BB17 BB25 DD03 EE10 GG01 GG02 GG12 GG14 KK01 5H621 JK01 JK19 PP05

Claims (6)

[Claims] 1. A bearing structure comprising a stationary member and a rotating member, wherein the stationary member supports the rotating member in a non-contact state when the rotating member rotates. A magnetic fluid is interposed between the two members on or near the rotation center axis of the rotation at which the relative rotation speed becomes minimum, and static electricity generated on the rotation side member during rotation is conducted to the fixed side member as needed. A bearing structure provided with a mechanism for causing the bearing to rotate. 2. The bearing structure according to claim 1, wherein the means for supporting the rotating side member in a state where the fixed side member is not in contact with the rotating side member is a dynamic pressure gas bearing. 3. A bearing structure comprising a fixed side member and a rotating side member, wherein the fixed side member supports the rotating side member in a non-contact state by dynamic pressure gas bearing means when the rotating side member is rotating. In the region where there is no or negligible airflow due to the suction or discharge of the gas necessary for the generation of the dynamic pressure, a magnetic fluid is interposed between the two members, and the static electricity generated on the rotation side member during rotation is optionally A bearing structure comprising a mechanism for conducting to a fixed-side member. 4. A bearing structure comprising a stationary member and a rotating member, wherein the stationary member supports the rotating member in a non-contact state when the rotating member rotates. Some or all of the components constituting the bearing portion are made of conductive ceramics, and when the rotation stops, the components constituting the bearing portion come into contact with each other, so that the static electricity accumulated in the rotating member during rotation is reduced to the fixed side. A bearing structure, wherein a mechanism for releasing the member is provided. 5. The bearing structure according to claim 4, wherein the means for supporting the rotation-side member while the fixed-side member is in a non-contact state is a dynamic pressure gas bearing. 6. The conductive ceramic material is Al.
_{2 0 3 -30vol% TiC, TiB} 2, Si 3 N 4 -30
The bearing structure according to claim 4, wherein the bearing structure is vol% TiN.